Pilot studies suggest a new approach to passive wireless biotelemetry for neural interfaces that may offer a breakthrough in size, weight, and power consumption. UHF band prototype devices involving only a very few active and passive components demonstrate the capability of an innovative back-scatter technology for telemetry of bioelectric events in 10 KHz bandwidths. In this project, we investigate the potential for a different paradigm in short range biotelemetry that achieves characteristics of small size and high performance not through silicon LSI techniques but by employing passive microwave circuits. Computer models using full wave electromagnetic simulations and nonlinear circuit analysis suggest that miniature devices designed for operation in the 5-10 GHz range can offer adequate levels of back-scattered signal and detectably transmit neuroelectric signals as low as 30 microvolts in amplitude. This suggests sufficient sensitivity for passive telemetry of cortical EEG and neural spike events. Miniature wireless neuroelectrodes will be made in this work using photolithographic tools and hybrid integration of commercial microwave components. This work will initially focus on demonstrating principles with a single channel device. We will characterize its sensitivity, range, and other qualities in-vitro using tissue-mimicking saline tanks. Implanted devices will wirelessly relay low level brain cortical potentials in acute experiments in rats. We will attempt to characterize and optimize the range and sensitivity performance of this approach for ultimate application to the more stringent radio frequency conditions of human implantation. This work will give insight into the potential for passive systems as a communications link for implantable multichannel neuroprostheses waveform data acquisition systems. This project is a step towards the long-sought goal of ultraminiature low power wireless devices directed towards high density wireless communication for neuroscience and neuroengineering investigators. PUBLIC HEALTH RELEVANCE This project seeks to develop a new type of RF-passive wireless biotelemetry system having the potential for high miniaturization and so suited to coupling to wholly implantable neuroelectrodes. This system uses microwave backscatter and the nonlinear properties of diodes for telemetry of biopotentials without resorting to complex analog or digital LSI techniques. We will investigate the effectiveness of this passive microwave telemetry device for transmitting neurological signals by designing and testing a prototype device that fits inside of a rat skull. Developments of the principles might eventually allow new designs of neuroprostheses useful in a wide variety of rehabilitation, clinical diagnostic, and man-machine interface applications.